Yield of bone scintigraphy screening for transthyretin-related cardiac amyloidosis in different conditions. Methodological issues and clinical implications

Background: Transthyretin-related cardiac amyloidosis (TTR-CA) is thought to be particularly common in specific at-risk conditions, including aortic stenosis (AS), heart failure with preserved ejection fraction (HFpEF), carpal tunnel syndrome (CTS) and left ventricular hypertrophy or hypertrophic cardiomyopathy (LVH/HCM). Methods: We performed a systematic revision of the literature, including only prospective studies performing TTR-CA screening with bone scintigraphy in the above-mentioned conditions. Assessment of other forms of CA was also evaluated. For selected items, pooled estimates of proportions or means were obtained using a meta-analytic approach. Results: Nine studies (3 AS, 2 HFpEF, 2 CTS and 2 LVH/HCM) accounting for 1375 screened patients were included. One hundred fifty-six (11.3%) TTR-CA patients were identified (11.4% in AS, 14.8% in HFpEF, 2.6% in CTS and 12.9% in LVH/HCM). Exclusion of other forms of CA and use of genetic testing was overall puzzled. Age at TTR-CA recognition was significantly older than that of the overall screened population in AS (86 vs. 83 years, p =.04), LVH/HCM (75 vs. 63, p <.01) and CTS (82 vs. 71), but not in HFpEF (83 vs. 79, p =.35). In terms of comorbidities, hypertension, diabetes and atrial fibrillation were highly prevalent in TTR-CA-diagnosed patients, as well as in those with an implanted pacemaker. Conclusions: Screening with bone scintigraphy found an 11–15% TTR-CA prevalence in patients with AS, HFpEF and LVH/HCM. AS and HFpEF patients were typically older than 80 years at TTR-CA diagnosis and frequently accompanied by comorbidities. Several studies showed limitations in the application of recommended TTR-CA diagnostic algorithm, which should be addressed in future prospective studies.